Zhang Li, Gao Man, Su Shilong, Zhou Zheng, Lee Hung Kay, Chen Xiao, Huang Zhifeng, Miao Qian
Department of Chemistry, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China.
State Key Laboratory of Synthetic Chemistry, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China.
Chemistry. 2025 Jul 8;31(38):e202501062. doi: 10.1002/chem.202501062. Epub 2025 Jun 6.
This study introduces two S-containing double helicenes capable of forming robust radical cations. These compounds were synthesized via the Scholl reaction, which was modulated to an intermediate stage by reducing the amount of oxidant, resulting in a sulfur-containing [7]helicene. X-ray crystallography analysis reveals that both S-containing double helicenes exhibit twisted conformations consistent with the global minima identified through density functional theory (DFT) calculations. Upon chemical oxidation with nitrosonium, these double helicenes produced π-conjugated radical cations, whose radical nature was confirmed using electron paramagnetic resonance spectroscopy. These radical cations remained stable in solution when exposed to air for several weeks, as monitored with absorption spectroscopy. One of the double helicenes forms π-stacked columns in the crystals of both neutral molecule and radical cation salt. The radical cation hexafluoroantimonate salt exhibits a room-temperature conductivity of up to 0.16 S cm, attributed to the significant π-π interactions observed in its crystal structure. This study indicates the potential of double helical π-skeletons as a versatile platform for developing resilient π-conjugated radical cations without compromising π-π interactions, with potential applications in organic electronics.
本研究介绍了两种能够形成稳定自由基阳离子的含硫双螺旋烯。这些化合物通过肖尔反应合成，通过减少氧化剂的量将反应调节到中间阶段，从而得到一种含硫的[7]螺旋烯。X射线晶体学分析表明，两种含硫双螺旋烯均呈现出扭曲构象，这与通过密度泛函理论（DFT）计算确定的全局最小值一致。在用亚硝酰离子进行化学氧化后，这些双螺旋烯产生了π共轭自由基阳离子，其自由基性质通过电子顺磁共振光谱得到证实。通过吸收光谱监测发现，这些自由基阳离子在暴露于空气中数周的情况下在溶液中仍保持稳定。其中一种双螺旋烯在中性分子和自由基阳离子盐的晶体中均形成π堆积柱。自由基阳离子六氟锑酸盐在室温下的电导率高达0.16 S/cm，这归因于在其晶体结构中观察到的显著π-π相互作用。本研究表明，双螺旋π骨架作为一个通用平台，在不损害π-π相互作用的情况下开发具有弹性的π共轭自由基阳离子具有潜力，在有机电子学中具有潜在应用。
